The present application is a continuation-in-part of co-pending Provisional U.S. patent application Ser. No. 60/020,914 filed Jun. 28, 1996. The entire text of the above-referenced disclosure is specifically incorporated by reference herein without disclaimer.
1. Field of the Invention
The present invention relates generally to the fields of polymers and high density compositions. More particularly, it concerns materials that may act as a replacement for lead in applications requiring lead""s high density, but where the toxic effects of lead are undesirable. Further, the high density composites of the present invention may be employed in any application where a high density material is required.
2. Description of Related Art
Each year, approximately 689 million rounds of small arms ammunition (.22 caliber through .50 caliber) are fired during training by the Army, Navy, Air Force, Marine Corps, National Guard, and Reserves in the United States. An additional 10 million rounds are fired annually by the Department of Energy. The ammunition projectiles used for this training consist of lead antimony cores, or cores, encased in a copper alloy jacket. Use of these projectiles results in approximately 2,000 tons of lead per year being introduced into the environment. Lead contamination of soil, sediments, surface and groundwater have been confirmed through investigations conducted at Army, Navy, Air Force, Marine Corps, Coast Guard and private small arms ranges throughout the United States and Europe. Lead uptake in vegetation at a Marine Corps small arms range in Quantico, Virginia showed lead levels as high as 23,200 parts per million. Remediation of contaminated ranges has proven to be extremely expensive and provides only a temporary solution. The Navy reports hazardous waste removal from one small arms firing berm cost $2.5 million with an additional $100,000 per year required for lead contamination monitoring. Sixteen Navy small arms firing ranges are now required to improve hazardous waste maintenance at a predicted cost of $37.2 million. In addition, the September 1995 xe2x80x9cCost Analysis for Munitions Rulexe2x80x9d prepared by the U.S. Army Concepts Analysis Agency indicate the cost to remediate an outdoor small arms range is approximately $150,000 per acre. Currently there are 120 ranges closing or scheduled to be closed as a result of Base Realignment and Closure recommendations which account for an estimated 4,185 acres or a total of $627 million.
In order for firing ranges to remain open, expensive cleanup procedures must be employed that provide only a temporary solution to the problem. A non-toxic, lead-free, environmentally safe, cost effective replacement projectile core material is required to enable firing ranges to remain open and to eliminate costly cleanup procedures. The density of the projectile should be close to that of a lead projectile for realistic performance simulation. Materials of a lower density decrease projectile range and penetration.
In addition, there is mounting concern over the use of lead shot for bird hunting, due to ingestion of the shot by birds and other animals as well as contamination of wetland areas. Indeed there has been legislation in the United States and other countries which bans the use of lead shots in waterfowl shots. Moreover, such a lead substitute or high density material will find many other applications, such as for weights, acoustic dampening or vibration dampening, and in radiation shielding applications, including protective clothing, medical clothing and clothing for use in nuclear reactors.
The present invention, in a general and overall sense, concerns a family of materials that may act as a replacement for lead in applications where the high density of lead is important, but where the toxicity of lead is undesirable. Thus there is presented in a particular aspect a high density composite for use in applications in which lead or any other high density material may be required.
Thus in a particular embodiment, there is provided a high density composition of matter, comprising tungsten powder, a fiber and a binder material. In particular embodiments, the tungsten comprises between about 5% and about 95% of the composite. In other embodiments, the tungsten comprises between about 10% and about 80% of the composite. In other embodiments, the tungsten comprises between about 15% and about 70% of the composite. In alternate embodiments, the tungsten comprises between about 25% and about 50% of the composite. In other embodiments, the tungsten comprises between about 35% and about 40% of the composite. Of course these are exemplary percentages and the tungsten may comprise any percentage between these figures, for example, about 5%, 6%, 7%, 8%, 9%, 12%, 14%, 16%, 20%, 21%, 22%, 23%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 42%, 44%, 46%, 48% 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%, 72%, 74%, 76%, 78%, 82%, 84%, 86%, or 88% of the composite weight.
In other aspects of the present invention the tungsten powder particle size is between about 2 and about 40 microns in diameter. In an alternative embodiment the tungsten powder particle size is between about 4 and about 8 microns in diameter. In yet another embodiment, the tungsten powder particle size is between about 20 and about 40 microns diameter. Of course these are exemplary measurements and the powder may comprise a particle size of about 4, 5, 6, 7, 9, 10, 11, 12, 14, 16, 18, 21, 22, 23, 24, 25, 28, 30, 31, 32, 33, 34, 35, 36, 37, 38 or 39 microns in diameter. In certain embodiments, it may be desirable to have tungsten powder comprised of particles having varying sizes of diameter. In other embodiments, the powder may be comprised of particles of uniform size of diameter.
In a particular embodiment of the present invention, the fiber may comprise stainless steel, copper, aluminum, nylon, Kevlar(copyright), Spectra(copyright), nickel, glass or carbon. In more particular aspects, the fiber is stainless steel fiber. In preferred embodiments, the fiber comprises between about 3% and about 30% of the composite weight. In other aspects the fiber comprises between about 10% and about 20% of the composite weight.
In alternate embodiments, the fiber comprises between about 15% and about 18% of the composite weight. Of course these are exemplary percentages and the fiber may comprise any percentage between these figures, for example, about 4%, 5%, 6%, 7%, 8%, 9%,10%, 12%, 14%, 16%, 19%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, or 29% of the composite weight.
In yet another aspect of the present invention the binder is a polymeric binder. In particular aspects the polymeric binder may be selected from the group consisting of cellulose, fluoro-polymer, ethylene inter-polymer alloy elastomer, ethylene vinyl acetate, ionomer, nylon, polythermide, polyester elastomer, polyester sulfone, polyphenyl amide, polypropylene, polyvinylidene fluoride or thermoset polyurea elastomer.
In more particular embodiments, the polymeric binder is Nylon 12(copyright) and polyester elastomer. In more specific embodiments the polymeric binder comprises between about 1% to about 30% weight ratio of the composite. In other embodiments, the polymeric binder is at a concentration of about 2% to about 20% weight ratio. In still further embodiments, the polymeric binder comprises between about 5% to about 15% weight ratio of the composite. In other embodiments, the polymeric binder comprises between about 8% to about 12% weight ratio of the composite.
The present invention further provides a high density plastic composition comprising a mixture of a base metal powder, fiber and binder. In particular embodiments, the base metal powder may be osmium, iridium, platinum, rhenium, tungsten, gold, tantalum, rhodium, palladium, thallium, silver, molybdenum, bismuth, copper, cobalt, nickel, cadmium, niobium and iron. In particular embodiments the high density composition may be utilized as a radiation shielding material. In other embodiments, the radiation shielding material is a flexible shielding material. In further embodiments, the composition may be utilized as modeling weights, fishing weights, flywheels, or projectiles.
Other objects, features and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.